1. Field of the Invention
The present invention relates to an external rearview mirror with a retention device, especially for an automobile, and, more particularly, to a retention device for the external rearview mirror of an automobile designed to provide better performance and utilization than the similar prior art devices.
2. Prior Art
External rearview mirrors are already known comprising a mirror; a casing housing the mirror; a supporting arm on which the casing is pivotally mounted at one end thereof; a base mounted on one side of a vehicle including retaining elements or a pivot for pivotally mounting the supporting arm; a torque adjusting device for adjusting a required torque necessary to move the arm in relation to the base and a retention device for securing the arm in a predetermined fixed position relative to the base.
In its known conventional form, the retention device may comprise a frame for adjacent portions of the arm and holding member of the base and arm that mutually interconnect in an axial direction, urged by a spring with a locking device.
This type of retention device, depending of the characteristics of the mirror, may be comparatively complex, so that its manufacture is complicated.
On the other hand, this type of structure for the retention device is subject to the effect of the weight of the arm, casing and mirror and of the vehicle motion.